1. Field of the Invention
The present invention generally relates to vehicle dynamics systems and road gradient determination systems associated with the navigation systems, and in particular to new techniques using model based systems for parameter observation.
2. Description of the Related Art
In recent modern navigation systems, it is crucial to distinguish between roads possibly lying on top of each other, which can be found in large cities. The navigation systems require highly reliable information about the road gradient in addition to vehicle positions on plain. For this it is necessary to detect the transition from one road level to another road level.
Conventionally, various road gradient determination systems have been proposed (for example, see Patent Document 1: JP 06-249655 A and Patent Document 2: JP 11-351864 A).
In the road gradient determination systems applied to conventional navigation systems or the like, it is impossible to provide sufficiently accurate position information in respective areas of roads. Therefore, it has not been possible to carry out the accurate gradient determination.